A Bored Electrician to Answer Your Questions

hey IamS5oned...

good to have a bored electrician on the boards... I got a question that maybe you could help me with...

I run my grow room with a PLC... it turns on the fans, lights, water pumps, and monitors the door switch and some other stuff... I run a closet in a small house, so its gotta be super stealth. So - i used to have 2, 1000w systems in there, and used these little solid state relays to turn them on/off. The solid state relays are rated at 25A at 240v (they will work with 120v too) they turn on with a DC signal voltage that comes from the PLC...

well - i'm having some rather odd problems with my PLC... mainly just one problem, when its not connected to the computer - its not really running.. it will not turn things on at the right time with no computer connected to it... (like it forgets the time or something)...

so here's the thing - when the solid state relays fail - they get hot, and then when you remove the DC signal voltage, the relay is so hot or whatever, that the load current will not stop... my question is - could the load current go back through the DC voltage lines into the PLC at some point? they failed a few times before i figured out what was going on, so they lights ran an extra hr or two on some days.

i had the relays mounted on a piece of aluminum with some small fans blowing on them and some thermal compound behind them so they aluminum would dissipate some of the heat... but still they arent quite enough to run the 1000w systems.... i changed up my closet to 2 digital quantum ballasts at 600w each - and i had a couple of instances during veg that the solid state relays failed again...

also, is there something i can do using 2 relays to turn on one light? I'm wondering if i can take the load wire, and split it, run it to 2 different SSR's and use 1 DC control wire to turn both SSR's on at the same time... will that divide the load through each SSR?

I never really understood the downsides of SSR's until i bought 50 of them - i love the fact that they are dead silent though Thanks for any info you might have...

thx mon, it has 3 ballasts- Advance Centium ICN 2S54 the lamps are sylvania pentron 6400k 54w. t5's . somehow, somewhere, we have to incorporate a timer, we know the fixture and bulbs are all good.

is my off the rack heavy duty digital timer, purchased at home depot. safe for what its been used for. 1000w mh and a carbon filter. its rated 1875w, the old school guy always used these heavy duty oversized overweighted timers in his time. 15 years ago. am i safe?

cloned said:

thx mon, it has 3 ballasts- Advance Centium ICN 2S54 the lamps are sylvania pentron 6400k 54w. t5's . somehow, somewhere, we have to incorporate a timer, we know the fixture and bulbs are all good.

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all you should need are a couple wirenuts, two single pole switches a double gang outlet box,some power, a piece of 14/3* long enough to go from the switches to the fixture, and the following two diagrams. enjoy

*you need an extra conductor because of the extra switch.


buy a simple plug in garden timer from a hardware store... see the diagram where it says 14/2 supply? put a male cord end on the wire there, and plug it into the timer... plug the timer into the wall

wow thats great, but i have a twist. i wanted to wire this straight to the panel. the timer would have to be somewhere in between. as close to the switches if possible. can i run a plug directly from the panel and then plug into that? of course i can. can't i? i have a special place in my heart for trades people. i'm a certified journeyman painter in canada. you sparkies are good people.

BloodShot420 said:

hey IamS5oned...

good to have a bored electrician on the boards... I got a question that maybe you could help me with...

I run my grow room with a PLC... it turns on the fans, lights, water pumps, and monitors the door switch and some other stuff... I run a closet in a small house, so its gotta be super stealth. So - i used to have 2, 1000w systems in there, and used these little solid state relays to turn them on/off. The solid state relays are rated at 25A at 240v (they will work with 120v too) they turn on with a DC signal voltage that comes from the PLC...

well - i'm having some rather odd problems with my PLC... mainly just one problem, when its not connected to the computer - its not really running.. it will not turn things on at the right time with no computer connected to it... (like it forgets the time or something)...

so here's the thing - when the solid state relays fail - they get hot, and then when you remove the DC signal voltage, the relay is so hot or whatever, that the load current will not stop... my question is - could the load current go back through the DC voltage lines into the PLC at some point? they failed a few times before i figured out what was going on, so they lights ran an extra hr or two on some days.

i had the relays mounted on a piece of aluminum with some small fans blowing on them and some thermal compound behind them so they aluminum would dissipate some of the heat... but still they arent quite enough to run the 1000w systems.... i changed up my closet to 2 digital quantum ballasts at 600w each - and i had a couple of instances during veg that the solid state relays failed again...

also, is there something i can do using 2 relays to turn on one light? I'm wondering if i can take the load wire, and split it, run it to 2 different SSR's and use 1 DC control wire to turn both SSR's on at the same time... will that divide the load through each SSR?

I never really understood the downsides of SSR's until i bought 50 of them - i love the fact that they are dead silent though Thanks for any info you might have...

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do you have the battery connected to the plc?
most plc's need a battery, just like your pc at home, so they dont 'forget' there programming when the device is powered down.

as far as trying to divide the load between two solid state relays, it simply wont work, there are too many factors involved to attempt what is called a 'parallel feed' all of the load will go through just one of the two relays.. you can try but if you somehow pull that off succesfully there are a few scientists that want to speak to you, and you might end up employed by nasa it has to do with the nature of the ssr in itself, the lengths/size of the wire, the temperature, how many bends are in the wire, etc etc etc. too many factors to consider, and its just not worth investing the time to even think about it!

concerning the heat build up on your ssd's... thay get hot by nature, unfortunatly, and should always be screwed down on a flat, thick peice of metal that is larger than the footprint of the relay so it will act as a heat sink. a peice of solid aluminum barstock is perfect for this and is east to cut and drill if you need to. . you can find alot of info on ssr's and how to size heat sinks for them here
another thing that is causing them to heat up is the non-linear load charecteristics of the electronic ballasts. theres not much you can do to avoid it im afraid.

i understand why you went with ssr's if your going for a stealthy approach. however there not that stealthy if u have to have fans blowing on them... if it was me, i would go with what is called an ice cube relay... they are pretty quiet, especially the small ones. or you could get a bigger relay with a built in heat sink... there pricey but nice.. this one in particular is VERY nice:
http://www.wolfautomation.com/Product.aspx?ProductID=10339
id find another supplier tho... wolf automation is expensive! they never let you buy single items

rural hick said:

i dunno.
but if you have ever seen those brown square commercial parking lot light fixtures? some have a decal 25x and some have a decal 40x. i suppose the 25x is 250 watts. i can get all them fixtures i want to carry off. the regional electric utility sometimes they just throw the fixture away, with out any troubleshooting them at all.
those are HPS (high pressure sodium) correct?
and if a guy got several out of the dumpster, maybe luck would befell him and he would have a johnny cash HPS?
what usually goes bad in those fixtures? bulb only or bulb and something else? i just wonder why would they come down off the pole to be replaced by a newer unit?

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aint nothin like somethin fer free! lol

well theres lots of reasons the power companies could be trashing those lights.. could be there just old and ineffecient and there upgrading to more modern technology... or it could be there just trash! as far as them being HPS the easiest way to tell is to look at the lamp! if the lamps arent in them you can check ballast or the inside of the fixture, it should have the lamp rating on it somewhere.
as far as dumpster diving to get the lights... its how i git mine! lol... the most common things that goes bad besides the lamps are the starter(capiciitor) the socket the lamp screws into can also get wornout, and of course the ballast itself. some fixtures also have a thermal switch that shuts down or cools the lamp whenever e certain temp is achieved. best thing to do is grab a few and start experimenting... if you can get alot of junk fixtures the likelyhood of finding enough good parts is pretty high. you can google the ballast type and with a little looking find some good schematics out there! happy hunting and good luck!

cloned said:

is my off the rack heavy duty digital timer, purchased at home depot. safe for what its been used for. 1000w mh and a carbon filter. its rated 1875w, the old school guy always used these heavy duty oversized overweighted timers in his time. 15 years ago. am i safe?

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as far as safety is concerned... imo the old school heavy duty timeclocks are superior. even tho there big, noisey, and clunky ive ran across some that have switched 4000w+ for 20-30 years with out a single malfunction. gotta love tork!

cloned said:

wow thats great, but i have a twist. i wanted to wire this straight to the panel. the timer would have to be somewhere in between. as close to the switches if possible. can i run a plug directly from the panel and then plug into that? of course i can. can't i? i have a special place in my heart for trades people. i'm a certified journeyman painter in canada. you sparkies are good people.

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of course you can!
and as far as that goes, if your gonna go with the old school timer (i would) you can just wire it directly up to the timeclock and skip having to buy/add the receptacle altogether...

i have a 125v, 15a, heavyduty outdoor timer, 1875w capacity. i'm have a 1000w mh and a 640cfm exhaust/carbon filter running on the timer. the timer was purchased at home depot. are these timers ok or do i need some heavy duty thing.

cloned said:

i have a 125v, 15a, heavyduty outdoor timer, 1875w capacity. i'm have a 1000w mh and a 640cfm exhaust/carbon filter running on the timer. the timer was purchased at home depot. are these timers ok or do i need some heavy duty thing.

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how many watts or amps is the fan?

Iam5toned, thanks for starting this thread and sharing your knowledge and experience, it's very much appreciated.

My question relates to cloned's question about timers. A typical timer that you can buy at home depot, walmart, etc. is usually rated for 15 amps, which would indicate to me that it would be safe to use at the maximum continuous wattage that a 15amp circuit can safely handle (80% of 120v*15a = 1440W). I have two 600w HPSs that have an input wattage of 630w each, so technically, this timer should be able to handle switching those two lights (1260w). However, when doing some research before I set up my room, I had read that ballasts pull an INDUCTIVE load, while these cheaper timers specifically state that they are designed for RESISTIVE loads only (I had also read that this is why cheaper timers burn out after so many cycles). Because of this and my strict safety standards (I definitely don't want a fire in the grow room!!), I opted for the intermatic T101 40A industrial timer that specifically states that it is capable of switching both resistive and inductive loads up to 40 amps @ 120v. That seems a little overkill for what I needed but I figured, better safe than sorry. So my question is, did I make the right decision by getting the more robust timer? Please explain.

highpsi said:

Iam5toned, thanks for starting this thread and sharing your knowledge and experience, it's very much appreciated.

My question relates to cloned's question about timers. A typical timer that you can buy at home depot, walmart, etc. is usually rated for 15 amps, which would indicate to me that it would be safe to use at the maximum continuous wattage that a 15amp circuit can safely handle (80% of 120v*15a = 1440W). I have two 600w HPSs that have an input wattage of 630w each, so technically, this timer should be able to handle switching those two lights (1260w). However, when doing some research before I set up my room, I had read that ballasts pull an INDUCTIVE load, while these cheaper timers specifically state that they are designed for RESISTIVE loads only (I had also read that this is why cheaper timers burn out after so many cycles). Because of this and my strict safety standards (I definitely don't want a fire in the grow room!!), I opted for the intermatic T101 40A industrial timer that specifically states that it is capable of switching both resistive and inductive loads up to 40 amps @ 120v. That seems a little overkill for what I needed but I figured, better safe than sorry. So my question is, did I make the right decision by getting the more robust timer? Please explain.

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Well to make a very long, boring and technical story a little shorter and easier to read, the reason why you shouldnt max out the wattage on a cheap timer when using ballasts or other type of inductive loads is a phenomenom known as 'blowback voltage'. on resistive loads, the inrush current is converted into heat or light, on inductive loads, the inrush current is often converted into voltage, which then will find the shortest path to opposite POTENTIAL. since a/c current reverses polarity 60 times a second, often the shortest path to an opposite polarity is right back up the wire it came in from, hence the term 'blowback' blowback voltage occurs on inductive loads when the magnetic field in an inductive device collapses during startup of the device. when the collapse occurs, it creats a very high voltage spike, it only lasts a nanosecond or two but it does occur. typicaly cheap timers are not engineered to absorb that voltage, so when the blowback occurs it can create an arc inside the timer and pit or scar the contact points on the relay. over time this decreases the conductivity of the contact points inside the relay which causes the relay to heat up when current is passing through it, and eventually you have a component failure. some modern solid state or optical relays have a preventative measure engineered into the design, it is a diode that acts as a check valve for the blowback....

as far as the case of your timer, i say you made the right choice. unless size or stealth is a very major factor in the design of your growroom setup, heavy duty electromechanical time clocks are the way to go. there reliability is superb, they are simple to program, and can last decades when used properly. although the wiring can often be more complicated in my opinion the trade off you have with reliability and safety is too good to pass by.

edit:
blowback does not typically occur when using modern digital ballasts. the blowback does occur inside a digital ballast, however it is isolated from the circuit by a diode. im not sure about cfl's*, but since i have grown several crops on the same cheap ass plug in timer using cfls* myself, it might not be a factor.

* i live in an apt so hid lighting is kinda out of the question for my budget and stealth concerns.

as far as the case of your timer, i say you made the right choice. unless size or stealth is a very major factor in the design of your growroom setup, heavy duty electromechanical time clocks are the way to go. there reliability is superb, they are simple to program, and can last decades when used properly. although the wiring can often be more complicated in my opinion the trade off you have with reliability and safety is too good to pass by.

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I'm not an electrician, but I consider myself to be pretty proficient at it. I framed and wired my basement myself, but I did get an electrician (who is a family friend) to come in and inspect it, and he gave me two thumbs up. So wiring the timer wasn't bad at all, sure it's not as easy as just pluging it in, but I'd rather spend the time to do it right, and be confident in my equipment. I guess I have no worries about blowback voltage as my two 600w ballast are digital, so that timer should last a long time. Thanks for the detailed response.

One more quick question if you would: I have a 700gph mag drive pump submerged in my reservoir on a digital timer, should I replace the outlet it is plugged into with a GFCI outlet? I'm always a little paranoid with a 120v line dropped into water (salt water to make matters worse!). I have heard of the odd circumstance where people have gotten a shock this way. The only reason why I haven't already installed a GFCI outlet is the potential for false positives, like a minor current fluctuation causing the GFCI to trip and then off goes my pump, which in turn, there goes my plants! Am I misinformed on this, what would you recommend?

Iam5toned, thanks so much for all the advice!

My question is related to a 400w HPS light. I got it from a small company that had a bunch left over from a previous job, fairly cheap. The only setback is that the ballast is attached to the top of the light, so I'll have to add in some extra fans to keep my closet cool once I install it.

The light however came with a twist lock plug. Obviously you just can't plug these into a normal socket. So I was going to just take off the plug and put a regular plug end on it. My concern was whether or not the light would operate by just making this change and plugging into a regular wall socket. The light has a label and says:
Voltage: 120 / 208/ 240/ 277 Amps: 4.3/ 2.48 / 2.15 / 1.86 And it's a S-51 lamp.

I just want to make sure I'm not going to start any fires if I try to plug this into a regular socket. Thanks in advance!

highpsi said:

I'm not an electrician, but I consider myself to be pretty proficient at it. I framed and wired my basement myself, but I did get an electrician (who is a family friend) to come in and inspect it, and he gave me two thumbs up. So wiring the timer wasn't bad at all, sure it's not as easy as just pluging it in, but I'd rather spend the time to do it right, and be confident in my equipment. I guess I have no worries about blowback voltage as my two 600w ballast are digital, so that timer should last a long time. Thanks for the detailed response.

One more quick question if you would: I have a 700gph mag drive pump submerged in my reservoir on a digital timer, should I replace the outlet it is plugged into with a GFCI outlet? I'm always a little paranoid with a 120v line dropped into water (salt water to make matters worse!). I have heard of the odd circumstance where people have gotten a shock this way. The only reason why I haven't already installed a GFCI outlet is the potential for false positives, like a minor current fluctuation causing the GFCI to trip and then off goes my pump, which in turn, there goes my plants! Am I misinformed on this, what would you recommend?

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A good,name-brand 20amp rated gfci receptacle will not trip on minor fluctuations with submerged pumps . i use them to supply power for submerged pumps (700gpm, a lot bigger than what your working with) on water features (a little side business of mine) all the time with no incidents.

the thing you want to avoid however is whats called an ARC FAULT type receptacle or circuit breaker. Recently incorporated into the NEC as a required device for bedroom receptacles in residential construction, arc fault breakers/devices are known to nuisance trip all the damn time, and are in my opinion pieces of shit not worth the packaging they came in!

lol go with a good name brand gfci (such as Pass Seymour Legrand or Leviton) and you cant go wrong

Tmac123 said:

Iam5toned, thanks so much for all the advice!

My question is related to a 400w HPS light. I got it from a small company that had a bunch left over from a previous job, fairly cheap. The only setback is that the ballast is attached to the top of the light, so I'll have to add in some extra fans to keep my closet cool once I install it.

The light however came with a twist lock plug. Obviously you just can't plug these into a normal socket. So I was going to just take off the plug and put a regular plug end on it. My concern was whether or not the light would operate by just making this change and plugging into a regular wall socket. The light has a label and says:
Voltage: 120 / 208/ 240/ 277 Amps: 4.3/ 2.48 / 2.15 / 1.86 And it's a S-51 lamp.

I just want to make sure I'm not going to start any fires if I try to plug this into a regular socket. Thanks in advance!

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welllll they put plugs on High Bay Lights (thats whats the HID fixture you have is called) for lots of reasons, but the main one is that so maintenance can easily remove the light from the circuit for repairs or placement issues.

Changing the nema(twistloc) cord-end is really a simple operation. Some things to keep in mind-
when removing the old nema cord end, cut the wires off the old plug, and leave enough attatched to the old plug so you can tell what wire goes to what blade on the new cord end. (trust me on this one, its a common mistake) we tells this to helpers/apprentices in the field because its really easy to hook up a cord cap wrong, and since its not the funnest job you like to only do it once.... its nice to have a piece of reference material

your ballast is what we call a multi-tap ballast, it can be used on a wide type of voltages. however sometimes this means the correct wire has to be made up to the hot leg on the cord; you will have to take the cover off of the ballast to see what your working with here. a newer digital ballast should have a single set of wires, if thats the case your good to go. an older mechanical style ballast will have a wire for each type of voltage... the voltage type is printed on the wire insulation. make sure the wire that says 110 110 110 110 is connected to the 'hot' on the cord, and not any other. its quite common for high bay lights to run off of 240 or 277, it saves money on the power bill. unfortunatly it wont work for you though... make sure you check!

and finally- just because the ballast is on top of the light fixture now, doesnt mean it has to stay there you can make it remote.....

IAm5toned said:

welllll they put plugs on High Bay Lights (thats whats the HID fixture you have is called) for lots of reasons, but the main one is that so maintenance can easily remove the light from the circuit for repairs or placement issues.

Changing the nema(twistloc) cord-end is really a simple operation. Some things to keep in mind-
when removing the old nema cord end, cut the wires off the old plug, and leave enough attatched to the old plug so you can tell what wire goes to what blade on the new cord end. (trust me on this one, its a common mistake) we tells this to helpers/apprentices in the field because its really easy to hook up a cord cap wrong, and since its not the funnest job you like to only do it once.... its nice to have a piece of reference material

your ballast is what we call a multi-tap ballast, it can be used on a wide type of voltages. however sometimes this means the correct wire has to be made up to the hot leg on the cord; you will have to take the cover off of the ballast to see what your working with here. a newer digital ballast should have a single set of wires, if thats the case your good to go. an older mechanical style ballast will have a wire for each type of voltage... the voltage type is printed on the wire insulation. make sure the wire that says 110 110 110 110 is connected to the 'hot' on the cord, and not any other. its quite common for high bay lights to run off of 240 or 277, it saves money on the power bill. unfortunatly it wont work for you though... make sure you check!

and finally- just because the ballast is on top of the light fixture now, doesnt mean it has to stay there you can make it remote.....

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Well Lets see if I can get this thing to start working before going remote....

Secondly, once I get the plug swapped over and everything is set to go. How long will it take to actually turn ON once I plug it in. Someone said that you'll hear it humming right away but that it'll take a while to see light. So, how long on average, before we can see light?

Tmac123 said:

Well Lets see if I can get this thing to start working before going remote....

Secondly, once I get the plug swapped over and everything is set to go. How long will it take to actually turn ON once I plug it in. Someone said that you'll hear it humming right away but that it'll take a while to see light. So, how long on average, before we can see light?

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well different lamps start differently too... mh tends to gradually brighten in intensity while hps will glow dimly for awhile then ignite quite rapidly

man the biggest factor that effects the length of lamp startup is temperature. the higher the ambient temp the quicker the lamp comes on. also the newer the ballast the faster the lamp will ignite. you should see a small glow almost instantly, however on either mh or hps. usually with temps in the room temperature range you can expect to have full lamp ignition in no longer than 90 secs.

Tmac123 said:

Well Lets see if I can get this thing to start working before going remote....

Secondly, once I get the plug swapped over and everything is set to go. How long will it take to actually turn ON once I plug it in. Someone said that you'll hear it humming right away but that it'll take a while to see light. So, how long on average, before we can see light?

Click to expand...

well different lamps start differently too... mh tends to gradually brighten in intensity while hps will glow dimly for awhile then ignite quite rapidly

man the biggest factor that effects the length of lamp startup is temperature. the higher the ambient temp the quicker the lamp comes on. also the newer the ballast the faster the lamp will ignite. you should see a small glow almost instantly, on either mh or hps. usually with temps in the room temperature range you can expect to have full lamp ignition in no longer than 90secs